Research
PLUS: A Detector-Agnostic Subspace Signal for Near-OOD Detection
The paper introduces PLUS, a post-hoc signal that complements existing out-of-distribution (OOD) detectors to improve near-OOD detection. PLUS builds per-class low-dimensional subspaces from sparse autoencoder decoder directions and scores inputs via whitened squared Mahalanobis distance. Fused additively with any calibrated base score at a fixed global weight, it improves near-OOD AUROC across all 126 detector-backbone combinations tested, while largely maintaining far-OOD performance.
out-of-distribution detectiondeep learninganomaly detection